A purified toxin from cholera bacteria slowed colorectal cancer growth in mice while sparing healthy tissue. The findings could inspire a new class of treatments that turn bacterial weapons into cancer-fighting tools.
A toxin produced by cholera bacteria has been shown to slow the growth of colorectal cancer in mice without detectable harm to the rest of the body, raising hopes for a new kind of targeted cancer therapy.
In a new experimental study, researchers at Umeå University in Sweden report that a purified bacterial substance called MakA, secreted by the cholera bacterium Vibrio cholerae, can both kill cancer cells and rally the immune system against tumors.
Colorectal cancer, which affects the colon and rectum, is the third most common cancer worldwide and the second leading cause of cancer death. Standard treatments such as surgery, radiation and chemotherapy save many lives but often come with serious side effects, and cases of colorectal cancer are rising globally. That has scientists searching for more precise and less damaging options.
The Umeå team focused on MakA, a cytotoxin — a molecule that can kill cells — that cholera bacteria naturally produce. Instead of using it as a weapon against infection, the researchers explored whether it could be repurposed as a weapon against tumors.
In mouse models of colorectal cancer, they administered purified MakA systemically, meaning it was delivered throughout the body rather than injected directly into tumors. They found that tumor growth was significantly reduced.
The toxin did not appear to spread damage indiscriminately. According to the study, MakA accumulated specifically in tumor tissue, where it increased the death of cancer cells and reduced their ability to multiply. At the same time, it altered the tumor’s “microenvironment” — the complex mix of cells and molecules that surround and support a tumor.
Co-lead author Sun Nyunt Wai, a professor at Umeå University, explained that MakA does more than simply poison cancer cells.
“The substance not only kills cancer cells directly. It reshapes the tumour environment and helps the immune system to work against the tumor without damaging healthy tissue,” Wai said in a news release.
The researchers observed that MakA treatment boosted the number of innate immune cells inside the tumors, especially macrophages and neutrophils. These are front-line defenders of the immune system that can attack abnormal cells and help coordinate broader immune responses. Their increased presence in the tumors appeared to contribute to the slowdown in cancer growth.
Crucially, the treatment did not trigger harmful inflammation in the mice. Even after repeated doses, the animals showed no adverse effects on body weight, overall health or the function of vital organs, the team reported. That pattern suggests MakA’s effects were largely local and focused on the tumors, rather than causing widespread toxicity.
Further analyses showed that MakA stimulated the production of immune mediators inside the tumors — signaling molecules that can promote cancer cell death. At the same time, regulatory mechanisms that help protect surrounding healthy tissue remained in place, indicating a potentially favorable balance between attacking the tumor and limiting collateral damage.
Turning bacterial toxins into medicines is an emerging strategy in cancer research. Bacteria have evolved powerful molecules to invade hosts and evade immune defenses. Scientists are increasingly exploring how to harness or reengineer those same molecules to fight disease, including cancer, in a controlled way.
In this case, MakA’s dual action — directly harming tumor cells while reshaping the immune landscape around them — makes it especially intriguing. It hints at the possibility of therapies that not only shrink tumors but also help the body’s own defenses keep cancer in check.
Co-lead author Saskia Erttmann, an assistant professor at Umeå University, emphasized both the promise and the early stage of the work.
“Although more research is needed, the results clearly show an interesting path for developing a new type of cancer treatment, which utilizes substances that bacteria create to both kill cancer cells and strengthen the body’s own defences,” Erttmann said in the news release.
For now, the findings are limited to animal experiments. The researchers stress that more studies are needed to test MakA in additional models of cancer and to carefully evaluate its safety and effectiveness before any potential use in humans. That includes understanding the precise mechanisms by which MakA targets tumors, how best to deliver it, and whether it could be combined with existing treatments such as chemotherapy or immunotherapy.
The study, published in the journal Cell Death and Disease, adds to a growing body of work suggesting that the microscopic world of bacteria may hold unexpected tools for fighting one of humanity’s deadliest diseases. If future research confirms MakA’s potential, a toxin once associated with a devastating infectious disease could one day help patients battling colorectal cancer.
Source: Umeå University